A solid polymer type fuel cell is attracting attention to be used for a cell automobile and a portable power supply since it is compact and can obtain a high current density when operated at room temperature compared with a phosphoric-acid type fuel cell and a molten carbonate type fuel cell. Further, many proposals on components, system compositions and the like in such fields have been made. A stack structure of a conventional solid polymer type fuel cell is a sandwich structure of, for example, of separator/electrode (oxygen electrode)/electrolyte membrane/electrode (hydrogen electrode)/separator. Required characteristics of an electrode for this fuel cell are to prevent the electrode from poisoning by carbon monoxide and to enhance activity per unit amount of a catalyst metal. For the purpose of preventing such poisoning and enhancing the activity, many trials have been made to date on metals or alloys thereof to be used as catalysts as described in JP-A-2001-85020 (U.S. Pat. No. 6,689,505), which describes that a particle size of a catalyst is preferably several nm.
On the other hand, as for carbon to be used for a carrier, particulate carbon such as ordinary carbon black is used as described in JP-A-8-117598, JP-A-2003-201417 (EP 1309024) and JP-A-2001-357857. However, since the contact between carbon particles is conducted by a point contact, there is a problem that resistance is large and gas permeability is insufficient. In order to solve these problems, it has been considered effective to change the particulate carbon to fiber carbon to be used for the carrier as described in JP-A-7-262997, JP-A-2003-317742 and JP-A-2003-200052.
As for carbon fibers, a vapor-grown carbon fiber, a carbon nanotube and a PAN type carbon fiber are known. However, in any of reports which have been made public to date, a technique to produce an electrode comprising a carbon fiber on which fine catalyst particles are uniformly carried with a high density has not been described.